Switching device



July 18, 1933. G. A. RITCHIE SWITCHING DEVICE Filed April 5, 1932 2 Sheets-Sheet l M/VENTOR G. A. R/ TCH/E ATTORNEY July 18, 1933.

G. A. RITCHIE SWITCHING DEVICE Filed April 5. 1932 FIG. 4

as T W Wi*w as i ,7

2 Sheets-Sheet 2 FIG. 5

ATTORNEY Patented July 18, 1933 UNEE'E TBS GEORGE RZTCHIE, OF BROOKLYN, Ll

i ATTE NT YORK, ASSEGNOR TO BELL 'nznnggonp YORK SWITCHJNG DEVICE Application filed April 5, 1932. Serial No. 603,344.

This invention relatesto circuitmakersand breakers and particularly to h] ghly insulated switches employed in controlling testing-circuits.

In order to determine Whether or not electric circuits in general, and telephone circuits particularly. are operating at a maximum eiiicicncy and to locate and rectify unstandard cond tions which may exist and which tend to interfere vith the eflicient operation of equipment associated with the circuits, it is neccz that the circuits vbe subjected to periodic tests. One of thechief sources of: trouble in telephone systems-is current leakin telephone cable circuits which, it al.- l. ed to persist, would seriously impair the t ansmission characteristics of the. circuits. It requires constant vigilance :to guard against the growth of such a condition.

In locating current leaks .in telephone cables various testing circuits .are in general use. To insure accuracy inthe tests .made with such circuits it is essential that the :apparatus employed be of such a design as to offer no low resistance current paths, jsoatha-t the measurements made will not be affected by the equipment employed; in making the tests.

t is the object of this invention to insure against leakage currents in apparatus employed in locating current leaks in telephone cables.

This object is attained in accordance with a feature of the invention by the provision of a circuit controlling switch which is highly insulated, durable. compact and simple inconstruction and which is quickly and conven iently operated.

In switches of the character herein disclosed. it is necessary that a'current leakage guard be employed and the contact members be located at a relatively great distance from the guard in order to insure adequate resistance to current leaks. It is also essential that the contacts be sufticiently segregated to prevent lealts therebetween. The purpose of the guard to permit lay-passing: some of the leakage which may occur along the surface of the insulators employed in the switch struc ture.

The switch contemplated bythis invention embodies a pantograph operating-mechanism interposed between the operating-lever and the movable or active contact carrying parts and so proportioned relatively to the movable parts as to insure the necessary movement of the latter and maintain sufiicient -resistance throughout the switch structure as toreduce to a i'ninimum the possibility of current leakage between the various elements of the of Fig. 1 looking in the direction of the arrows;

Fig. 5 is a sectiou ataken along-the l ine*5*5 of Fig. 1 looking in the directionof the arrows;

Fig. 6 shows schematically,.a wheatstone bridge testing circuit of which the-iswitch shown in Figs. 1 to 5 inclusive, and 7,-io1zms a part when the bridge is .employedin testinga telephone tollline; and Y Fig. 7 is a section taken along the line of Fig. 1 looking in the direction of ,the arrows.

Like numerals throughout the several figures indicate similar parts.

The switch mountingplateris madeqip of a phenol fibre plate 10 superimposed on a metal plate 11 and secured thereto oy-means of screws or in any other sui -table manner. The members 10 and 11 are centrally apertured to provide a slot 12 through Which an operating lever 13 extends. Secured 'to the under side of plate 11 are two brass mounting brackets 14 which are centrally bridgedibya pin 15 upon which the lever 13 is adapted to pivot, the lever being secured to the rivet blade 26.

f f T member 16 which is provided with a central bore which serves as a housing for the midportion of pin The lower portion of the lever 13 is bifurcated to provide a slot gener ally indicated by the numeral 17, the purpose of which will hereinafter appear.

Interposed between the horizontal member 18 of a metallic guard and the metal plate 11 are four petti-coated insulating supporting members 19, there being two at either extremity of the switch.

The stationary or passive contact members 20 of the switch are mounted on petti-coated insulating members 21 by means of screws 22. The insulators 21 are rigidly secured to the guard member 18 by means of screws 23. Two sets of contact members 20 are provided,

one OII Bltl-IGI side of the pair of petti-coated way of the two pairs of contact carrying insulators 21 as shown in Fig. 1.

The centrally disposed insulators 24 are each provided with a centrally projecting ,pushfitting bifurcated bolt 25, each of which supports a pivotal contact rocker arm or knife The knife blade 26 is centrally positioned on the bolt 25 and is pivotally supportedin the slot effected by the bifurcated end of the bolt on a pin 27.

Interpos'ed between the operating lever 13 and the mcvable or active contact member 26 is a pantograph operating mechanism which acts as a medium through which the move ment of the lever 13 is communicated to the contact member or rocker arm 26.

The 'pantograph mechanism consists of two inverted U-shaped elements 28 which, with member 18 and pins constitute the guard. .one located near each end of the member 18, andinsulat-ing cross bars 29, 30, 31 and 32. The two Ushaped members 28 are pivotally supported on pins 33each of which is carried bya pair of oppositely disposed upturned lugs-or cars 34 which are integral portions of the guard member 18.

The insulating bars or members 29, 30, 31 and'32zare joined at their ends and supported by theguard pins 35 which pass through each leg of the U-shaped guard members 28 as clearly seen in Fig; 4. Metallic washers 36 are interposed between adjacent insulating rods and between the insulating rods and the vertical legs of the U-shaped member 28. The pins 35, insulating bars 29, 30, 31 and 32 and the washers 36 are so assembled as to permit the insulating bars to pivot on the pins 35 when the U-shaped members are actuated, as will. appear from a later description. A small circular groove is provided at each end ofth'e pins 35 which accommodate the circular-springs 37. These springs prevent the pins 35 from working out of position.

to form a centrally located slot. At the midpointof the insulating bars 29 and 32 there is provided a screw 41 provided with a head 42 having an annular groove 43 into which the two ears freely fit. By virtue of the engagement of the cars 40 with the groove 43 of screw head 42, any movement of the insulating bars 29 and 32 is imparted to the knife blade 26.

To facilitate the making of external circuit connections with the contact members 20 and 25, spring members 44 and 45 are provided. A spring terminal 46 is also provided for the guard member 18 and is secured thereto by means of a screw 46 which with corresponding screws 47 serve to secure the guard member 18 to the insulators 19 which are interposed between the guard member 18 and the metal frame member 11.

Having described the construction of the switch embodying the features of this invention, its operation will now be explained.

Normally, the switch assumes a position shown by the full lines of Fig. 1 with the knife blade 26 in a horizontal position and disengaged from either set of stationary contacts 20. Assuming it is desirable to effect a circuit connection between the spring terminals 45 and the left hand terminals 44, the lever 13 is thrown to the right to the position indicated by the broken or dash lines in Fig. 1.

The lever 13 pivots about the pin 15 whereupon the pin 38 and insulating bars 30 and 31 experience a lateral movement to the left due to the fact that the pin 38 and its associated collar 39 are confined within the slot 17 effected by the bifurcated end of lever 13. Theinsulating bars 30 and 31 being loosely or rotatably secured to the insulating bars 29 and 32 respectively, at both ends and with the U-shaped guard members 28 by means of guard pins 35, the bars 29 and 32 move simultaneously with, and in the same direction as the bars 30 and 31, the guard members 28 moving angularly to the left about their respective pivot pins 33.

The screws 41 being rigidly secured to their respective insulating rods 29 and 32 move to the left therewith and in so doing cause the knife blades 26 to pivot about the pins 27 by virtue of the engagement of the depressed annular portion of the screw heads 42 with the cars 40. The left hand end of knife blade 26 is accordingly forced down into engagement with the left hand contact springs 20 so that mmense :3

the terminal springs-4 L and areelectnically connected by way of the cOntactispringsQO, left hand portion of :knife .blade 26 land springs 25.

The methods of returning the switch to normal and of effecting a connection between terminal springs l?) and the right hand terminal springs 44 are obvious.

Fig. 7 discloses the method employed by applicant in centering the lever li'liin its normal position. The brass mounting brackets 1 are each provided with a cylindrical bore. the outer portion of which is of'a greater diameter than the inner portion andis tapped to receive the screw 50. The inner portionof each bore houses a small coil springfil and a small steel ball The lever 13 is provided with a small cylindrical. bore 53 of smaller diameter than that of the steel balls 52 and is so located on the lever 13 that when the latter is in its normal position the axes of the lever bore 53 and the two bores in the mounting brackets l l are in alignment. In normal position of the levr, therefore, the spring l l forces its respective ball into the end of the lever bore 53 tending to maintain the lever in this position.

Referring to Fig. 6., there s disclosed a simple i'heatstone bridge circuit which is generally employed in testing telephone toll lines and with which the switch just described finds particular application. This c rcuithas been shown for the purpose of describing the use of a guard in the switch structure.

The circuit shown to the right of terminals A, B represents a telephone toll line and the ground X indicates the location of an un standard condition on this line. Assuming the apparatus associated with the \Vheatstone bridge is impervious to current leaks, which is the ideal condition, the currents I and I would be equal, and by adjusting the movable arm, a balance, as indicated by the galvanonieler (i, may he obtained. Then, by a series ot computations well known in VVheatstone bi lgc circuits, the ict location of the current leak X, may be obtained. Should the equipment he p'iorly insulated and unguarded, a lead: to ground shown at Y might occur. It is obvious that the current 1,, will be increased by the current tlow through Y to ground. This causes an unbalance in the circuit and in order to restore the balance, the movable arm C would have to be adjusted until the galvanoinetcr t} showed a ZQIIi readng. This causes an inm'curate location of lll': leak X to be computed, rendering the test wholly unreliable. However, when the equipme: gin rded by the shield 18. the leakage current instead cl finding a ready path to ground, is rendered inetlcctive in producing any ap 'ireciable eli ect on the galvanometer reading. The path through the insulating cicments oi the switch which is purposely deagned to present a high resistance, generally in the neighborhood of ten thousand imegohms, is now connected in parallel with .the arm :of the VVihGfltStOIIQ ibridge through which thecunrent 1 is .flowing. For practicalpurposesthe resistance ofzthis armis designed-to be five thousand ohms so that the associated insulating bars '30 and 31 are not connected directly to knifeblades 26 for effecting the-actuation thercofas such a construction would provide a relatively short path from the spring contacts 25-to the operating lever, when normal or from either of the contacts 20 to the lever when actuated should the lever become accidentally grounded. The path of such a leakage currentto an accidentally grounded lever includes one-half of :the insulating bar 29, a relatively long path and one .of very high resistance.

Theutility-of applicants specially devised guard arrangement is clearly shown in Fig. 4. The guard consistsprimarily of the horizontalplatealS, itsassociated integral ears 3.4, U-shaped members 28-and the pins 3.3. Each of these elements is at guard potentialaso that thepins introducesuch a potential at the ends of'thezhorizontal-rods 29 to inclusive, andithereforeibetween the actuatinglever li'l anditliedniife blade contacts 26. The potential is applied to the guard by Way of the terminal 55.

Other structural details which increase the insulating characteristics of the switch are evident from the foregoing description.

What is claimed is:

1. In a switching mechanism, a stationary contact, a movable contact member, an operating lever for effecting the engagement of said movable contact member with said stationary contact, and a pantograph mechanism interposed between said movable contact member and said operating lever for transmitting the movement of said operating lever to said movable contact member, said pantograph mechanism comprising a pair of pivotally movable end members and a plurality of insulating bars pivotally secured thereto, said operating lever being associated with one of said bars at its midpoint and said movable contact member being associated with another of said bars at its midpoint.

2. In a switching mechanism, a stationary contact, a movable contact member, an operating lever for effecting the engagement of said movable contact member with said stationary contact, insulating rods interposed between said movable contact member and said operating lever for transmitting the movement of said operating lever to said movable contact member, and a current conducting guard pivotally supporting said insulating rods.

3. In a switching mechanism, a stationary contact, a pivotally movable contact, an insulating bar having its mid-point in operative engagement with said movable contact, a second insulating bar having an end mechanically coupled with an end of said first insulating bar and an operating lever in operative eiwagenieiit with the mid-point of said second insulating bar for moving both said bars linearly as a unit to cause said movable contact to pivotally move into engagement with said stationary contact.

l. In a switching mechanism, a mounting plate, a pair of brackets secured to said mounting plate, a pin bridgin said brackets, an operating lever pivotally mounted on said pin and protruding from said mounting plate, a. guard, a plurality of elongated insulators interposed between said mounting plate and said guard and secured thereto, a plurality of insulating members carried by said guard each supporting a stationary contact member, said insulating members being interposed between said mounting plate and said guard, a pair of vertically extending supports pivotally mounted on said guard, one on either side of said plurality of insulating members, a plurality of insulating bars supported between said supports in superposed relation to said stationary contacts and adapted to move horizontally upon the pivotal movement of said supports, a knife blade pivotally mounted on one of said insulating members and provided with a pair of centrally located ears, a pin joining certain of said insulating bars and normally engaged by said ears, a pin joining other of said insulating bars and normally resting in a slot in said lever whereby the movement of said lever is transmitted to said knife blade, to effect engagement between said knife blade and said stationary contacts through the medium of said insulating bars.

5. In a switching mechanism, a stationary contact, a movable contact member, an operating lever, an insulating bar associated with said operating lever and actuated thereby, a second insulating bar associated with said movable contact member, and a guard, said insulating rods being secured together at their ends through the medium of a pin forming a portion of said guard whereby the movement of said operating lever is transmitted to said movable contact member to eliect an engagement between said movable contact member and said stationary contact.

6. In a switching mechanism a stationary contact, a movable contact, an operating lever, means for transmitting the movement of said lever to said movable contact to effect engagement between said movable and stationary contacts, said means comprising two insulating members joined at their ends by a metallic pin, and a current conducting guard conductively associated with said pin whereby guard potential is introduced between said operating lever and said contact members.

GEORGE A. RITCHIE. 

